1. Field of the Invention
This invention relates to an electrolytic cell and a process for utilizing the electrolytic cell to achieve the labeling of proteins, peptides and other organic molecules. More particularly, this invention relates to an electrolytic cell and a process for utilizing the electrolytic cell to achieve the radiolabeling of proteins, peptides and other organic molecules.
2. Description of Related Art
Present techniques for labeling proteins, peptides and other organic molecules with halogens or other labels suffer from several drawbacks. Chemical labeling processes, for example, often are difficult to scale-up and tend to damage the proteins and peptides which are to be labeled. In addition, because these same chemical labeling processes may have low yields, unreacted label has to be separated from the labeled material. While this purification step not only makes chemical labeling processes less efficient, in the case of radioactive labels it exposes the operator to a hazardous substance. Among the current processes for radiolabeling proteins is solid phase iodination which employs oxidative techniques for producing an electrophilic iodine species (I.sup.+) from sodium iodide.
Present electrochemical techniques for labeling proteins, peptides and other organic molecules with halogens or other labels, such as technetium and rhenium, suffer from other drawbacks. For example, electrochemical labeling processes often use platinum or gold as the anode and cathode of the electrolytic cell. Using current electrochemical techniques, biological materials can be iodinated on a microgram scale with up to 80% incorporation of radioiodine. In order to get short reaction times, many workers use a relatively high ratio of anode surface area to electrolyte volume. This high ratio of anode surface area to electrolyte volume is commonly accomplished by using a platinum crucible which functions as the reaction vessel as well as the anode. Platinum crucibles, however, are inadequate for commercial operation for a number of reasons. For example, platinum crucibles are not practical because their geometry precludes maintaining a uniform potential across the anode surface, particularly in solutions of low conductivity. Also, their geometry does not allow easy variation of the surface area/electrolyte volume ratio. This is due to the fact that, for any shape, area does not increase as fast as volume. Further, these crucibles use relatively large amounts of platinum or gold which must be either thrown away after each use or subjected to cumbersome cleaning procedures which generate liquid radioactive waste.
Present electrochemical techniques also suffer from drawbacks similar to chemical techniques. For example, in the context of the commercial production of radiolabeled monoclonal antibodies (MAbs), the anodes, cathodes, membranes, and other components of the electrolytic cell can become contaminated with the radioactive labeling agent. The cost of radioactive waste disposal makes it necessary to pay more attention to the efficiency of use of the isotope and to where it ends up when efficiency is less than 100%.